<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8" />
		<title>3.指定回调方式</title>
	</head>
	<body>
		<script type="text/javascript" >
			/* function demo(){
				alert(1)
			} */

			setTimeout(()=>{},1000)
		</script>
	</body>
</html>